The present invention is a single-chamber syringe having an internal valve-type closure actuatable by displacement of the plunger for administration of liquid products, especially medicinal products (medicament), which require the act of injection for administration thereof to a patient. More specifically, the present invention is drawn to a syringe belonging to the group which can be marketed with the product to be injected contained therein and are therefore known as disposable xe2x80x9cprefilled syringesxe2x80x9d, and are provided with the medicinal product contained therein to ensure that the user does not come into contact with the product.
Numerous syringes are known which have been produced for the same purpose as stated above. All of them are formed of a cylindrical and hollow main body within which is accommodated the medicinal product which is to be administered and within which a coaxially arranged plunger moves. In all these cases, the lower base of the main cylindrical body is opened and allows the displacement of the plunger. In general, they include a flange which projects to the outside and is used as a support point for the user to push or pull on the plunger. At the other end, the opposite base of the main cylindrical body defines a hollow and coaxial tip which is frustoconical and acts as a connecting or coupling for the attachment of the injection needle. Such a device is shown in U.S. Pat. No. 5,785,683.
The novelty which distinguishes this embodiment lies in the fact that the syringe includes a very special valve-type closure for keeping the liquid content isolated, the closure being designed to open or close, allowing or preventing the passage of fluid to the injection needle by displacement of the plunger.
Co-pending application Ser. No. 09/344,974 relates to a syringe having a double internal chamber, which is suitable for bringing about the mixing of two separate components by displacement of the plunger. The valve used is internal, so that it requires no modification to the main cylindrical body of the syringe or even the incorporation of special plugs to close its open base, permitting the displacement of the plunger without undesirable losses of content occurring. The valve which is accommodated within the main cylindrical body, divides the latter into two internal chambers of variable volume, so that the active head of the plunger simultaneously acts as the face closing the distal chamber.
On the other hand, in the case of the present application, the valve is not used to form two internal chambers but is designed to act as an upper hermetic closing for a single isolated chamber which contains the product.
In the case of the ""974 application, the novel internal valve uses two elastomeric portions which act by cooperating with one another, so that they mix the originally isolated components, when the plunger moves in a direction opposite to the injection action and allows the mixture to escape toward the injection needle when the plunger is displaced, performing the injection action.
The internal valve-type plug incorporated in the single-chamber syringe according to the present invention, is characterized in that it is arranged adjacent to the connecting cone of the syringe bearing on the internal face of its upper base, so that the projecting portion that it possesses, in this case, blocks communication with the injection needle, while the lower base of the internal body of the plug is the upper base of the internal chamber of the syringe which accommodates the liquid.
In this manner, when the user displaces the plunger, by pulling in the direction opposite to the injection direction, the internal body moves away from the periphery, opening communication to the needle. Once this communication has come about, the conventional method is followed of displacing said plunger in the injection action whereby the liquid flows toward the needle and, through the needle, to the outside, passing through the valve assembly.
An advantage over the known art lies in the fact that it is no longer necessary to include a plug in the connecting cone within which communication with the injection needle is established, since the valve plug itself produces hermetic sealing from the interior of the syringe.